Radio direction finder



July 21, 1931.` c. R. ENGLUND 1,815,246

RADIO DIREETION FINDER Filed Jne29. 1929 Flai/ TRA/VSM/ 77E?? PHASE 5 Y/ REcE/l/f/P FIG. 2 y f I l PH sf I l WR Qff- @spillo/4R0 By C.' :i [NGL .L1/v0 MTM/Ww systems for, radio direction indin v ing from lthe transmitter.

i' Whether of the ,which is attended by Patented July 2l, 1931 UNITI-:D STATES PATEN-.I onlcg CARI. mi ENGLUNIJQ or FREEHOLD, NEWl .T1msn/Y, AssIeNoR To BELL TELEPHONE nano- RATORIES, INCORPORATED, OF'NEW YORK, 1\`|'. Y., 'A CORPORATION' OF NEW` YORK RADIO DIRECTION FINDER Application filed :rime 29 This invention relates 'to It perhaps has its greatest utility in de ning the course of a mobile station, for example, an airplane, and for guiding such station along the course defined.

' Copending application of P. H. Evans and J. W. Greig, lSerial No. 362,900, filed May 14, 1929, assigned to my assignee, discloses andclaims subject matter genericto this patent.

In the art of radio direction finding, it has been common to employ communicating means between a mobile station and one or more fixed stations, involving the use of either a transmitter v'or a receiver at the mobile station to determine by triangulation the instantaneous position of the mobile sta-r tion with-respect to these xed stations and therefore to enable a course `to be set. While such means may insure the ultimate progress of a mobile Astation to its objective, it does not insure that 'such progress shall be in a direct line. Therefore, while in most instances such means are reasonably effective for the navigation of ships at seawhere relative movements may easily be measured, they are not so eii'ective in air navigation, relatively large side drift due to atmospheric currents which cannot easily be measured or ,corrected for. 'It has accordingly resultedthat for air navigation especially, it has become practically necessary to Ause a directive method or system in which paths may be fixedl detinitelywithrelation to the earth, thus elim# inating dependence on momentary direction determination. Thesepaths constitute reference lines or patterns which define courses for the mobile station. A simple method'of radio guidance of this kind,in use at present, involves localized, transmitting apparatus, and the course is a radio line extendin a radio method or system for detining a course and for guiding an object along it,

above, or of other type Within the same broad classification, naturally involves a means'whereby a positive indicao-,tion is obtained when the mobile station is methods of, orl

'- and those areas A requirement 1,929. serial Na. 374,655.

in its course and showing, by a I'change in its indication, in sense and t amount, any deviation from the course. The receiving circuit in the mobile station should also be adjustable so that any desired course relative to, those determined by the reference pattern may beset on the indicator.

In the method or system above described, a

the discriminationf between comprised between the lines of the pattern lines, is based on. thev relative ,amplitude characteristics of the Waves received in these respective areas, that is, on the directive characteristics of the transmitting station. Applicant conceived the idea of a somewhat similar method, but using phase insteadfof amplitude, discrimination, and certain inherent advantages in the same.

It is the principal object of the invention to'provide means for fixing adesired course more effectively than by-prior meth-, ods or means, and for following such course Awith less deviation..

In its simplest form the method involves Vthe use at thel mobile vreceiving station of a phase standard wave having the .same frel ,quency as that of the beacon wave. This ether areas which are contiguous tothe wave is adjustable both asy to phase and" amplitude so that, with respect to the indicator in the output circuit of the receiver, in.

tion) implies or attends arotating field set up bv the beacon station,

which continuously traverses' the genera.n area in which the receiveriisrto move, thv, principle of the invention is in a sensedis tinctly different from thatof 'the previousmethods 4in the same ample of whichhas 'which general class, an ex een described, anc

station, (which condition defines,l the vrequisite phase varia` or at least a fiel@ are principally-characterized bv thr.

employment. of a fixed radio pattern local y mobile object.

nectedA which has an ied over the earths surface. Since the resent invention is not dependent on any ich lixed pattern, there is no limitation as i thecourse which may be' set toward the bj ective, while preserving the benefits of the ull indication principle, this being a disinct advantage over prior systems. he peration of the method of the invention is .lso characterized by an inherently more .ensitive response to deviations of thenobile receiving station Jfrom the set course han byl the operation of .ng upon amplitude discrimination. This rneans that the mobile receiving station is ableto follow its'set course with less deviation.`

Other objects of the invention are therefore to provide methods and means whereby a mobile receiving station may more unerringly set and 'follow a desired course, andr with less sacrifice of accuracy 'and of sensitivity depending ofi 'the' choice of courses, than may be achieved by prior.

methods andmeans.

' In one ormof the avoid difficulties in synchronizing the beacon wave and the phase standard wave, the phase variation in the beacon wave may be translated into, and made use of in, a, reproduced modulating component of it,'the same modulations being impressed. on an independently radiatedwaveI at the beacon station and when reproduced at the mobile receiving station, used as the phase standard wave. Observations may be facilitated by giving the modulating wave an audible 'frequency, so that, for example, a telephone receiverv can be used Ias the indicating instrument.

In the drawings Fig. 1A shows a transmit- .ting station at a fixed point;

Fig. 2 shows alreceiving station which may be located on an airship orother mobile object Fig-3 shows another yform "of transmitting .station at a fixed point; and

Fig. 4` shows another. forni kof vreceiving station which may also lbe 'located on`a In the circuit frequenc 4 marked Radio f1 antenna 1. Connected to the output of the oscillation generator in parallel to the loopij' antenna 1 is a phase shifter inwhich the current received byphase 9 antenna' 2 which to a second loop the first loop 3X1;

is crossed with respect to tenna.- i

The circui of Fig. 1 broadcasts Aa wave asymmetrical phase characteristie, and maybe called a' rotating wave. v if the broadcasting.. station were circumnavigated during the interval :"f one cycle, at any given radius, and at a fixed .f l

methods dependtion, this phase relationship will invention, in order to:

.necessity of transmitting the v.device isshifted 0"., The output of the device is conspeed, in the direction of the rotation of the Iield, the wave received during the journey would not change' in phase.

InFig. 2 an antenna 3 receives the asymmetrical wavebroadcast from the crossed loops shown in Fig. 1. This wave is ampliied in an amplifier Amp f1 and fed into af synchroscope or other phase indicating device. Connected to the synchroscope is a phase standard oscillation generator f1 which generates a wave of the same frequency as the received wave incident on the antenna 3. At any instant of comparison of the two waves received by the synchroscope there willl be a definite phase relationship indicated between them. If the mobile receiving station is traveling in va straight line toward the transmitting staremain the phase indicatin deviceconstant, and

change in the 1n cation.

will show. no However, if the mobile gets off the direct course to the beacon wave. received mitting station will be received in a difierent phase relationship with respect to the reference standard wave generated locally the transmitter, from the transreceiving station and the synchroscope will indicate this v change, thus giving an indication that the mobile receiving station is oi 'its' course. and enabling the .pilot tomake the necessary adjustment of his directionv of motion.

Any suitable' method or means may used for generating the vbeacon wave at the transmitting vstation and the phase reference wave at the receiving station. A t present the most satisfactor means of 0btaining a wave of standard rquency is the use of a quartz crystal to control the frequenc of, oscillations, sion or maintaining stant temperature. Such devices have been with suitable provithe crystal at a conv used for synchronizing iapparatus in picture transmission4 and television tov obviate the a synchronizing wave between the sending and receiving stations. l l

It may be desired to avoid the necessity of having a, wave generating device on the mobile receiving station, in which case weight is an important factor. lf means :areprovided atthe transmitting station ferwbroadcasting aphase st andar provided at the receiving station for receiving both of these waves and phase relationship, the necessity'for a wave generator at the` receivingv station will be obviated. If the beacon moreover, there will he no dangerof a falsedue to variations in the frei l particularly if the ,f receiving station lis'located on an airship,l

wave as well-as a beacon wave,- and means are comparing their wave and reference wave are derived from the same s0urce,

must be broadcast on -diiferent wave lengths, however, so that they may be separately received for comparison purposes. It follows that the waves used must be sov chosen with respect to the various functions they are to l' perform Lthat the will not affect the indicaquency f1 `snpplies this wave to a vertical tion. Thatis, t e carrier waves mustjnot affect thephase relation of the waves. to be compar d at the point of reception.`

In F- g. 3 there is shown a tr'ansmittin stationwhich accomplishes this result. generator f1 High of a wave of radio freantenna 11,.located centrally with respect to a pair of crossed loop antennae12, 13. Waves from the generator f1 are also S11 plied to a modulating device Mod (1 where they are modulated with waves of a low frequency f2 im ressed thereon from a -low frequency osci lation generator4 f2 Low. The carrier and one slide band are suppressed in vthe modulatingl device and thev modulation component of frequency ffl-f2 or fi-fz is fed into the crossed loop antennae 12, 13, vthe ywave fed into loop an tenna 13 being first passed through a phase shifting devicev Phase shifter -where its hase is shifted 90 with 'respect to the wave ed into loop-12.' Waves from the oscillation generators f1. and f2 are also intermodu- 'lated in a second modulating device Mod.

(2),thevcarrier and ne side band (the 011ev alternative tol that uppre'ssed byC Mod. (1)) are suppresse and the other side band is fed into a non directive antenna 14,

v'which is located in pro mity 4to the crossed loops and central antenna, but notfnecessarilyin any fixed locatipn with respect thereto. `Of course, the functions of the two modulators may be combined Vin a single modulator having a divided 'outpnt circuit.

, In Fig'. 4 is shown diagrammatically appraratus for receiving the. wavesV broadcast om the transmitting apparatus of Fig. 3l and .obtaining the desired indication therefrom. The rotating wave of frequency fff yf, 1s received on an antenna 415 and iml pressed with the wave of frequency f1 .on a

detector'Det. iff-f2, Low frequency wave f2 in the output of the detector will have'the antennae have sufficient resolving f po L "fl'i'fm I" .l

-llationship of said rotatingwave and said.

equency fof. two Jdiiferent frequencies) andj isjm.

vpressed'togetherv vith the wave of frequency wave oflovgr l frequency f2' is detected." This v 'i' Wave will have 1a vsymmetrical phase char'- 1 ,-ateristic'withfrespectto all'thepoints equidistant f r-onrfthe transmitting antenna,

may'ndvv bei-'used a standard reference wave. This wave of frequency f; is also im,

pressed on the synchroscope, whichl gives any indication of "the phase relationship of the two waves of frequency'f, and-[enables'the 'pilot to direct his course in a strai ht lineA towardthe transmitting station. t of v course necessary that the .two rec iving discriminate between frequencies f2 andi` What isclaimed is:

1.' In combination, a pair antennae, a non-directional antenna locate Vcentrally with respect to said loops aseoond non-directional antenna,means for generta.:

of crossed'loo y .erating 'a Lwavo of radio frequency, means for generating a wave of low frequency, l

means for intermodulating said waves, means for transmitting one side band ofsaid intermodulated wave4 as a rotating wave from said crossed loop antenn, means for trans- ,mitting said wave` of radio frequency from said central non-directional antenna, and means Vfor transmitting the other vside band of said intermodulated waves from said secondfnon-directional antenna.

2. Incombination, means for transmitting a rotating wave as a side band of a moduf lated carrier wave, means for transmitting a reference wave as the other side band of said modulated carrler wave and means for.

receiving and intercomparing the phase rereference wave.

afrhe manga 5f' direction andmb a radio which comprises generating a frequency wave and a low -frequencyqwave, intermodulating said waves,' transmitting one `'side band of-said modulated wave as a rotatin wave, transmittingv the other side hand'o said modulated wave asa'non-'rotat- 'in wave separately receivingand'detectingl saigd side bands and intercomparing the" phase characteristics of said detected waves.

A In witness whereof, I hereunto subscribe` .my name this 18th dat,1 of June, 1929.

omnia. ENGLUNDL 

